Plasma processing method and plasma processing apparatus

ABSTRACT

A plasma processing method executed by a plasma processing apparatus includes a first step, a second step, and an etching step. In the first step, the plasma processing apparatus forms a first film on a processing target in which a plurality of openings having a predetermined pattern are formed. In the second step, the plasma processing apparatus forms a second film having an etching rate lower than that of the first film on the processing target on which the first film is formed, and having different film thicknesses on the side surfaces of the openings according to the sizes of the openings. In the etching step, the plasma processing apparatus performs etching from above the second film under a predetermined processing condition until a portion of the first film is removed from at least a portion of the processing target.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority from Japanese PatentApplication No. 2018-141742 filed on Jul. 27, 2018 with the Japan PatentOffice, the disclosure of which is incorporated herein in its entiretyby reference.

TECHNICAL FIELD

The following disclosure relates to a plasma processing method and aplasma processing apparatus.

BACKGROUND

As a miniaturization of semiconductor devices is progressed, researchand development of techniques that enable minute dimension processingare in progress. One of the techniques is the extreme ultravioletlithography (EUVL).

For example, a technique for smoothing the edge of a processing targetusing EUVL has been proposed (U.S. Patent Laid-Open Publication No.2016/0379824). In this technique, after forming a passivation layer thatis deposited preferentially in a recess of a processing target, aprotruding portion on which the passivation layer is not deposited isremoved by etching. The reason why the passivation layer is depositedpreferentially in the recess rather than the protrusion is that aspecific surface area of the recess is larger than the protrusion. Thistechnique is also considered to be effective in reducing the localcritical dimension uniformity (LCDU).

SUMMARY

A plasma processing method according to an aspect of the presentdisclosure includes: providing a processing target formed with aplurality of openings having a pattern; (a) forming a first film on theprocessing target; (b) forming a second film on the first, the secondfilm having an etching rate lower than that of the first film and havingdifferent film thicknesses on the side surfaces of the openingsaccording to the sizes of the openings; and (c) etching the second filmunder a predetermined processing condition until a portion of the firstfilm is removed from at least a portion of the processing target.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating an example of a flow of a plasmaprocessing according to a first embodiment.

FIG. 2A is a schematic cross-sectional view of an example of aprocessing target of the plasma processing according to the firstembodiment.

FIG. 2B is a schematic top view of the processing target illustrated inFIG. 2A.

FIG. 2C is a schematic cross-sectional view illustrating the state inwhich a first film and a second film are formed on the processing targetillustrated in FIG. 2A.

FIG. 2D is a view (1) for describing an etching removal rate of thefirst film and the second film deposited on the sidewall of an opening.

FIG. 2E is a view (2) for describing an etching removal rate of thefirst film and the second film deposited on the sidewall of an opening.

FIG. 3 is a diagram for explaining an LCDU improvement effect obtainedby the plasma processing method according to the first embodiment.

FIG. 4 is a diagram for explaining a relationship between film formingconditions and etching resistance.

FIG. 5 is a view illustrating an example of the processing sequence ofthe plasma processing according to the first embodiment.

FIG. 6 is a view illustrating another example of a processing sequenceof a plasma processing according to the first embodiment.

FIG. 7 is a view illustrating still another example of a processingsequence of a plasma processing according to the first embodiment.

FIG. 8 is a flowchart illustrating an example of a flow of a plasmaprocessing according to Modification 1.

FIG. 9 is a view illustrating an example of the processing sequence ofthe plasma processing according to Modification 1.

FIG. 10 is a view illustrating another example of the processingsequence of the plasma processing according to Modification 1.

FIG. 11 is a view illustrating still another example of the processingsequence of the plasma processing according to Modification 1.

FIG. 12 is a flowchart illustrating an example of a flow of a plasmaprocessing according to Modification 2.

FIG. 13 is a flowchart illustrating an example of a flow of a plasmaprocessing according to Modification 3.

FIG. 14 is a view illustrating an example of the processing sequence ofthe plasma processing according to Modification 3.

FIG. 15 is a view illustrating an example of a vertical cross section ofa plasma processing apparatus according to an embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. The illustrativeembodiments described in the detailed description, drawing, and claimsare not meant to be limiting. Other embodiments may be utilized, andother changes may be made without departing from the spirit or scope ofthe subject matter presented here.

First Embodiment

Variations in dimensions in semiconductor microfabrication affect theperformance of the final products. For example, consider the case offorming a gate electrode on a semiconductor substrate. First, apolysilicon layer for a gate electrode and a mask layer for etching aresequentially formed on a semiconductor substrate. A patterncorresponding to the gate electrode is formed on the mask layer throughlithography such as, for example, EUVL. Then, the polysilicon layer isetched using the mask layer to form a gate electrode. In this case, whenthere is a variation in the dimensions of patterns of mask layers, thevariation leads to the variation in the dimensions of gate electrodes asit is. For this reason, it is desirable to increase the uniformity ofpattern dimensions at the stage of the mask layer. In the firstembodiment, a technique of equalizing the dimensions of patterns formedon processing targets and improve the LCDU. In the plasma processingmethod according to the first embodiment, for example, when a pluralityof patterns having substantially the same dimensions are repeatedlyformed on the processing target, the dimensions of the patterns areequalized. The plasma processing method according to the firstembodiment also exhibits an improvement effect in the pattern roughnessof, for example, a semiconductor wafer.

<Example of Flow of Plasma Processing of First Embodiment>

FIG. 1 is a flowchart illustrating an example of a flow of a plasmaprocessing according to a first embodiment. The plasma processingaccording to the first embodiment is performed by, for example, a plasmaprocessing apparatus described later (see, e.g., FIG. 15).

First, a processing target (e.g., a wafer) in which a plurality ofopenings having a predetermined pattern are formed is disposed in aspace in which a plasma processing is to be performed. Then, the plasmaprocessing apparatus executes a first step (step S11). The plasmaprocessing apparatus forms a first film on a predetermined pattern ofthe processing target in the first step. Next, the plasma processingapparatus executes a second step (step S12). The plasma processingapparatus forms a second film in the second step. The second film isformed to cover the first film. Here, the deposition of the second filmis performed by setting processing condition such that the amounts ofthe second film deposited on the side surfaces of the openings varydepending on the sizes of the openings in the processing target. Inaddition, the deposition of the second film is performed by settingprocessing condition such that the etching rate becomes lower than thatof the first film. Next, the plasma processing apparatus executes anetching step (step S13). In the etching step, the plasma processingapparatus performs etching under the predetermined conditions on theprocessing target on which the first and second films have beensequentially formed until a portion of the first film is removed from atleast a portion of the processing target from above the second film.Then, the plasma processing apparatus determines whether or not theprocessing target is in the state in which a predetermined condition issatisfied (step S14). When it is determined that the predeterminedcondition is not satisfied (No in step S14), the plasma processingapparatus returns to step S11 and repeats the processing. Meanwhile,when it is determined that the predetermined condition is satisfied (Yesin step S14), the plasma processing apparatus terminates the processing.This is an example of the flow of the plasma processing according to thefirst embodiment.

<LCDU Improvement Obtained Using Loading Effect and Selection Ratio>

The plasma processing according to the first embodiment will be furtherdescribed with reference to FIGS. 2A to 2E. FIG. 2A is a schematiccross-sectional view of an example of a processing target of the plasmaprocessing according to the first embodiment. FIG. 2B is a schematic topview of the processing target illustrated in FIG. 2A.

The processing target illustrated in FIG. 2A includes a substrate SB, anetching target layer EL, and a mask layer MK. The etching target layerEL and the mask layer MK are sequentially formed on the substrate SB. Inaddition, a predetermined pattern is formed on the mask layer MK. Asillustrated in FIG. 2B, the predetermined pattern has a plurality ofsubstantially perfect circles in a top view, and the plurality ofsubstantially perfect circles are aligned at predetermined intervals.Three openings on a line V1-V1 in FIG. 2B are denoted by O1, O2, and O3,respectively. In addition, the widths of the openings O1, O2, and O3aligned along the line V1-V1 are denoted by W1, W2, and W3,respectively.

Here, in design, the openings O1, O2, and O3 have the same dimension,and the widths W1, W2, and W3 have the same length. However, when theabove pattern is formed on the mask layer MK through lithography suchas, for example, EUVL, the dimensions of respective openings may vary.For example, as W1<W2, W2>W3, and W1<W3, a variation may occur in thewidth dimensions of respective openings.

Therefore, the first step of the above embodiment is performed (FIG. 1,step S11). As an example, the first step is performed through chemicalvapor deposition (CVD) using a material having a loading effect to formthe first film. The loading effect means a phenomenon in which, forexample, the film thickness of a film to be formed differs according topattern density. For example, the sizes of openings after film formationvary according to a pattern size itself, for example, the opening areasof openings. In addition, the sizes of the openings after film formationvary according to the pattern shape and arrangement around the pattern.Since the film thickness varies according to the density of the patterndue to the loading effect, for example, as illustrated in FIG. 2C, thefilm thickness of a first film formed on the side walls T1 of a smallopening O1 is thin and a second film formed on the side walls T2 of alarge opening O2 is thick (see, e.g., FIG. 2C). FIG. 2C is a schematiccross-sectional view illustrating the state in which the first film andthe second film are formed on the processing target illustrated in FIG.2A. In FIG. 2C, the film thickness difference is shown more emphaticallythan the actual one for the sake of description.

Next, the second step of the above embodiment is performed (FIG. 1, stepS12). For example, as in the first step, a second film is formed throughCVD using a material having a loading effect. Then, similarly to thefirst film, a thin second film, which is thin on the side walls T1 andwhich is thick on the side walls T2, is formed (see, e.g., FIG. 2C).

Next, etching is performed on the processing target from the top onwhich the first film and the second film are formed (FIG. 1, step S13).First, the second film is etched away and gradually removed. At thistime, the second film formed on the side walls T2 is thicker than thesecond film formed on the side walls T1. Therefore, even if the secondfilm on the sidewalls T1 is removed by etching, the second film remainson the sidewall T2.

FIGS. 2D and 2E are views [(1) and (2)] for describing the etchingremoval rates of the first film and the second film deposited on thesidewalls of the openings, respectively. The first film having a filmthickness A and the second film having a film thickness B are depositedon the processing target side wall T2 illustrated in FIG. 2D. Inaddition, on the processing target side wall T1 illustrated in FIG. 2E,a first film having a film thickness a and a second film having filmthickness b are deposited. The magnitude relationship between the filmthickness values is A>a and B>b.

First, it is assumed that it takes 12 seconds to remove the second filmon the side wall T2 (film thickness B) by etching. In addition, it isassumed that it takes 10 seconds to remove the second film on the sidewall T1 (film thickness b) by etching. Then, when etching is performedfor 12 seconds on the entire processing target, the second film isremoved for 12 seconds on the sidewall T2, and then the first filmremains without being etched (removed film thickness is B). In contrast,on the sidewall T1, after the second film is removed for 10 seconds, thefirst film is further etched for 2 seconds. Therefore, the filmthickness removed on the side wall T1 is equal to the film thickness bof the second film plus the film thickness a of the first film removedby the etching for 2 seconds (removed Film thickness is b+a).

Here, when the etching rate of the first film and the etching rate ofthe second film are approximately the same, the film thickness removedby the etching on the side wall T1 is the same as the film thicknessremoved by the etching on the side wall T2 (B=b+α). However, when. theetching rate of the first film and the etching rate of the second filmare not approximately the same, a difference occurs between the totalamount of the film. thickness removed by the etching on the side wall T1and the total amount of the film thickness removed by the etching on theside wall T2 (B≠b+α).

For example, when the etching rate of the first film is higher than theetching rate of the second film, then B<b+α. In addition, while thechange in the film thickness on the side wall T2 before and after theplasma processing is A+B−B=A, the change in the film thickness on theside wall T1 is a+b−(b+α)=a−α. Then, while the width W2 of the openingO2 decreases by 2A, the width W1 of the opening O1 decreases by 2a−2α.That is, it is possible to reduce the opening size on the wide openingO2 side by a greater amount than on the narrow opening O1 side. It ispossible to further increase this effect by setting the etching ratesuch that the value of a increases. With this phenomenon, it is possibleimprove the LCDU of a processing target.

FIG. 3 is a diagram for explaining an LCDU improvement effect obtainedby the plasma processing method according to the first embodiment. Thevertical axis in FIG. 3 represents the opening size of openings, and thehorizontal axis represents a processing time. The solid line representsthe change in the opening dimension between the side walls T1 of theopening O1, and the dotted line represents the change in the openingdimension between the side walls T2 of the opening O2 (see, e.g., FIG.2C).

First, in the opening O1, when the first step is initiated at time to,the first film starts to be deposited on the sidewalls T1. During thefirst step, the opening dimension gradually decreases, and at time t1when the first step is terminated, the opening dimension decreases fromWA1 before the processing to WA2. Next, when the second step isinitiated at time t1, the second film starts to be deposited on thesidewalls T1 of the opening O1. During the second step, the openingdimension gradually decreases, and at time t2 when the second step isterminated, the opening dimension further to WA2.

Meanwhile, in the opening O2, when the first step is initiated at timet0, the first film starts to be deposited on the sidewalls T2. Duringthe first step, the opening dimension gradually decreases, and at timet1 when the first step is terminated, the opening dimension decreasesfrom WB1 before the processing to WB2. Next, when the second step isinitiated at time t1, the second film starts to be deposited on thesidewalls T2 of the opening O2. During the second step, the openingdimension gradually decreases, and at time t2 when the second step isterminated, the opening dimension further to WB3.

Next, when the etching step is initiated at time t2, the second film isgradually removed from the opening O1, and the opening dimensionincreases. At time t3, the second film deposited on the sidewalls T1 ofthe opening O1 is completely removed by etching to expose the firstfilm. Since the etching rate of the first film is higher than theetching rate of the second film, the rate of increase in the openingdimension, that is, the rate of removing the film by etching increasesafter time t3. The opening dimension of the opening O1 at time t5 whenthe etching process is terminated becomes WA4.

Meanwhile, in the opening O2, when the etching step is initiated at timet2, the second film is gradually removed as in the opening O1, and thusthe opening dimension increases. However, since the opening dimensionWB1 of the opening O2 at the processing initiation time t0 is largerthan the opening dimension WA1 of the opening O1, the thicknesses of thefirst and second films deposited by the loading effect is thicker in theopening O2 than in the opening O1. Therefore, all the second film isremoved in the opening O2 at time t4 after time t3. After the time pointt4, the etching of the first film is also initiated in the opening O2.The opening dimension of the opening O2 at time t5 when the etchingprocessing is terminated is WB4.

As can be seen from FIG. 3, the dimensional difference between theopening O1 and the opening O2 at the processing termination time t5(WB4−WA4) is decreasing compared with the dimensional difference betweenthe opening O1 and the opening O2 at the processing initiation time t0(WB1−WA1). In particular, since the etching rate increases after theremoval of the second film (time t3) in the opening O1, the dimensionaldifference is rapidly decreasing. From this, by increasing the etchingselection ratio of the first film and the second film, it is possible toquickly eliminate the dimensional difference between the openings.

<Relationship between Loading Effect and LCDU Improvement Effect>

Next, the relationship between the loading effect and the LCDUimprovement effect will be described. For example, as illustrated inFIG. 2C, it is assumed that an opening O1 and an opening O2 having anopening dimension larger than that of the opening O1 are formed in aprocessing target. In addition, the film thickness of the first filmdeposited in the first step and the film thickness of the second filmdeposited in the second step are a and b in the opening O1 and A and Bin the opening O2, respectively. In addition, the etching selectionratio between the first film and the second film (the ratio of theetching rate of the first film to the etching rate of the second film,i.e., the etching rate of the first film/the etching rate of the secondfilm) is assumed to be S.

At this time, when all the second film is removed in the opening O1, thefilm thickness of the second film remaining in the opening O2 is (B−b).Then, when all the second film remaining in the opening O2 is removed,the thickness of the first film remaining in the opening O1 is(a−(S×(B−b))). Then, the difference between the opening dimension of theopening O2 and the opening dimension of the opening O1 is reduced by(A−(a−(S×(B−b))) (=LCDU improvement amount). Here, by substituting A−a=Xand B−b=Y into the above equation, the LCDU improvement amount may beexpressed by Equation (1) as follows.(X+(S×Y))  Equation (1)

From Equation (1), it can be said that as the values of X and Y arelarger, the LCDU improvement amount becomes larger. That is, for eitherof the first film and the second film, as the loading effect (X, Y) islarger, the LCDU improvement amount becomes larger. That is, the largerthe difference in film thickness (X, Y) between the first film and thesecond film formed in the openings O1 and O2, the larger the improvementamount of the LCDU. Further, when there is a loading effect (X, Y) forany one of the first film and the second film, an improvement in theLCDU is expected. In addition, when the second film has a loading effect(Y) and the etching selection ratio (S) between the first film and thesecond film is large, a large improvement effect is expected.

<Example of Non-Using Loading Effect>

In the example of FIG. 3, the film thicknesses of the first film and thesecond film formed in the opening O1 and the opening O2 are controlledto be different using the loading effect. Without being limited thereto,for example, the first film may be formed by a method that does not usethe loading effect, and only the second film may be formed using theloading effect. For example, the first film may be formed using atomiclayer deposition (ALD).

When there is a difference between the thicknesses of the second filmsformed in the opening O1 and the opening O2, a deviation is causedbetween the etching initiation times of first films. Thus, a differencemay occur in the film thickness between the films to be finally etchedin the opening O1 and the opening O2. For this reason, even if the firstfilm is formed without using the loading effect, it is possible to enjoythe effects of the present embodiment.

<Etching Rate and Processing Condition>

FIG. 4 is a diagram for explaining a relationship between film formingconditions and etching resistance. The example illustrated in FIG. 4represents that it is possible to obtain the selection ratio even if thefirst film and the second film are formed of the same material. Thevertical axis in FIG. 4 represents an etching rate (nm/min), and thehorizontal axis represents an O₂ addition flow rate (sccm) at the timeof film formation.

The film forming conditions used in the example of FIG. 4 are asfollows. In addition, among the following conditions, the applied powersare indicated in the order of the applied power for generating plasmaand the applied power for generating bias voltage.

-   -   The pressure in the chamber: 10 mT    -   Applied power: 1000 W+0 W    -   Gas type and flow rate: SiCl₄/He/O₂=25/100/@ @ sccm    -   Processing time: 60 seconds

The etching conditions used in the examples of FIG. 4 are as follows.

Example 1

-   -   The pressure in the chamber 20 mT    -   Applied power: 500 W+100 W    -   Gas type and flow rate: C₄F₈/Ar=40/200 sccm

Example 2

-   -   The pressure in the chamber 20 mT    -   Applied power: 500 W+50 W

As can be seen from the examples of FIG. 4, even in the case of formingthe same SiO₂ film, it is possible to change the etching rate bychanging the addition flow rate of O₂. In the examples of FIG. 4, theetching rate is higher as the O₂ addition flow rate is smaller, and theetching rate is lower as the O₂ addition flow rate is higher. Therefore,after the SiO₂ film is formed as a first film by setting the O₂ additionflow rate low, it is possible to form the SiO₂ film as a second film bysetting the O₂ addition flow rate high. Although the etching selectionratio varies according to the types of etching gases, in the examples ofFIG. 4, it is possible to control the etching selection ratio within therange of about 1 to 17 for the same SiO₂ film.

<Processing Sequence Example 1>

FIG. 5 is a view illustrating an example of the processing sequence ofthe plasma processing according to the first embodiment. In the firststep, a SiO₂ film is deposited as a first film by CVD using SiCl₄ and O₂as processing gases. In the second step as well, a SiO₂ film isdeposited as a second film by CVD using SiCl₄ and O₂ as processinggases. However, in the second step, the etching rate of the first filmis adjusted to be higher than the etching rate of the second film byincreasing the flow rate of O₂ compared to that in the first step. Theetching step is performed using NF₃. Thus, in the plasma processingmethod according to the first embodiment, it is possible to form thesame type of films as a first film and a second film by changing theprocessing condition in the first step and the second step.

<Processing Sequence Example 2>

FIG. 6 is a view illustrating another example of a processing sequenceof a plasma processing according to the first embodiment. In the firststep, a first carbon film is deposited as a first film by CVD using afirst type of carbon-containing gas as a processing gas. The first typeof carbon-containing gas is, for example, a CF-based gas. The first typeof carbon-containing gas is, for example, C₄F₈ or C₄F₆. In addition, thefirst type of carbon-containing gas is, for example, a CHF-based gas.The first type of carbon-containing gas is, for example, CH₂F₂ or CH₃F.In the second step, a second carbon film is deposited as a second filmby CVD using a second type of carbon-containing gas as a processing gas.The second type of carbon-containing gas is, for example, a CH-based gassuch as, for example, CH₄. The etching step is performed using O₂. Arare gas such as, for example, Ar may be used in the first step, thesecond step, and the etching step.

<Processing Sequence Example 3>

FIG. 7 is a view illustrating still another example of a processingsequence of a plasma processing according to the first embodiment. Inthe first step, a carbon film is deposited as a first film by CVD usinga carbon-containing gas as a processing gas. For example, a CF-basedgas, a CH-based gas, or a CHF-based gas may be used as a processing gas.In the first step, a SiO₂ film is deposited as a second film by CVDusing SiCl₄ and O₂ as processing gases. The etching step is performedusing NF₃.

As described above, the plasma processing method according to the firstembodiment may be executed by combining various gas types. In addition,the film types of the first film and the second film may be the same.

<Number of Cycles>

In the plasma processing method according to the first embodiment, thefirst step, the second step, and the etching step are performed as onecycle, and a plurality of cycles are performed until a predeterminedcondition is satisfied. The predetermined condition is, for example,that a dimensional difference between the plurality of openings formedin a processing target has become equal to or less than a predeterminedvalue, or that a predetermined number of cycles have been executed.

<Film Type, Gas Type, Etc.>

In the first embodiment, the film types of the first film and the secondfilm have been described as, for example, SiO₂, or a carbon-containingfilm (e.g., CF-based film, a CH-based film, or a CHF-based film).However, without being limited thereto, the first film and the secondfilm may be, for example, silicon-containing films such as, for example,a silicon oxide (SiO_(x)) film, a silicon nitride (SiN) film, a siliconcarbide (SiC) film, and a silicon (Si) film. In addition, the first filmand the second film may be, for example, a titanium (Ti)-containing filmor a tungsten (W)-containing film. In addition, the first film and thesecond film may be, for example, boron-containing films.

As the gas type used in the etching step, when the film to be etchedcontains silicon or metal, a halogen-containing gas is suitable. Whenthe film to be etched is a carbon-containing film, an oxygen-containinggas may be used as the etching gas.

<Etching Method>

In addition, in order to etch the sidewalls in the etching step, forexample, isotropic and anisotropic etching, plasma etching, or atomiclayer etching (ALE) may be used. In addition, in the etching step, theprocessing condition for etching may be changed when the second film isremoved and at least a portion of the first film is exposed. Forexample, the removal rate of the first film by etching may be furtherincreased by changing the processing condition of etching from the firstprocessing condition suitable for etching the second film to the secondprocessing condition suitable for etching the first film. For example,at the time when at least a portion of the first film is exposed, theetching gas type may be changed to accelerate the etching rate of thefirst film.

In addition, by modifying the first embodiment, etching may be performedafter depositing a film, of which the etching rate is lower than that ofthe mask layer MK (see FIG. 2A), on the mask layer MK using the masklayer MK itself as the first film. Then, the LCDU may be improved byvarying the etching amount of the mask layer MK different according tothe position. Further, instead of the two layers of the first film andthe second film, a film of two or more layers may be formed. In thatcase, a difference in etching rate may be provided between the films. Inthis case as well, the etching rate is also set such that the etchingrate becomes lower for a film on the outer side.

In the first embodiment, the pattern in which a plurality of perfectcircles illustrated in FIGS. 2A and 2B are aligned has been described asan example. However, the present embodiment is not limited to thepattern of the shape illustrated in FIGS. 2A and 2B, and may be appliedto improve the variation in the LCDU or the line shape of an ellipticalpattern. For example, the present embodiment may be applied animprovement in line edge roughness (LER) and line width roughness (LWR).

Effect of First Embodiment

The plasma processing method according the first embodiment includes afirst step, a second step, and an etching step. In the first step, theplasma processing apparatus forms a first film on a processing target inwhich a plurality of openings having a predetermined pattern are formed.In the second step, the plasma processing apparatus forms a second filmhaving a lower etching rate than the first film on the processing targeton which the first film is formed, in which the film thicknesses on theside surfaces of the openings are different according to the sizes ofthe openings. In the etching step, the plasma processing apparatusperforms etching under a predetermined processing condition until aportion of the first film is removed from at least a portion of theprocessing target from above the second film. Therefore, according tothe plasma processing method of the first embodiment, it is possible toimprove LCDU using a loading effect and a difference between the etchingrates of the first film and the second film. The plasma processingmethod according to the first embodiment may be applied to theimprovement of the LCDU of a pattern manufactured using extremeultraviolet lithography (EUVL).

In addition, in the plasma processing method according to the firstembodiment, the predetermined processing condition in the plasmaprocessing apparatus is changed from the first processing condition tothe second processing condition at the time when the first film isexposed in at least a portion of the processing target in the etchingstep. For example, in the plasma processing apparatus, the removal rateof the first film by etching may be further increased by changing theprocessing condition of etching from the first processing conditionsuitable for etching the second film to the second processing conditionsuitable for etching the first film. Therefore, with the plasmaprocessing apparatus, it is possible to further improve the improvementeffect of the LCDU.

Further, in the plasma processing method according to the firstembodiment, the first step, the second step, and the etching step arerepeatedly executed in the plasma processing apparatus until it isdetermined that the predetermined condition is satisfied. Thus, theplasma processing apparatus is capable of executing the processing untilthe desired LCDU is achieved.

<Modification 1—Formation of Gradient Composition Film>

In the first embodiment, the LCDU is improved by forming each of thefirst film and the second film and then performing etching. InModification 1, the film deposition condition is changed while forming asingle layer film, thereby achieving the same effect as forming the twofilms of the first film and the second film in the first embodiment.

FIG. 8 is a flowchart illustrating an example of a flow of a plasmaprocessing according to Modification 1. The plasma processing accordingto Modification 1 is performed in, for example, a plasma processingapparatus described later (see, e.g., FIG. 15).

First, like the plasma processing according to the first embodiment(see, e.g., FIG. 1), a processing target (e.g., a wafer) in which aplurality of openings having a predetermined pattern are formed isdisposed in a space in which a plasma processing is to be performed. Theplasma processing apparatus executes a deposition process (step S81). Inthe deposition step, the plasma processing apparatus deposits a film onthe pattern under a processing condition that the etching rate of thedeposited film gradually decreases as the distance from the processingtarget increases. In addition, the film thickness of a film deposited inthe deposition step varies according to the sizes of the openings due toa loading effect. Next, the plasma processing apparatus executes anetching step (step S82). Then, the plasma processing apparatusdetermines whether or not the processing target is in the state in whicha predetermined condition is satisfied (step S83). When it is determinedthat the predetermined condition is not satisfied (No in step S83), theplasma processing apparatus returns to step S81 and repeats theprocessing. Meanwhile, when it is determined that the predeterminedcondition is satisfied (Yes in step S81), the plasma processingapparatus terminates the processing. This is an example of the flow ofthe plasma processing according to Modification 1.

<Processing Sequence Example 1>

FIG. 9 is a view illustrating an example of the processing sequence ofthe plasma processing according to Modification 1. In the example ofFIG. 9, a SiO₂ film is deposited as in the example of FIG. 5. First, inthe deposition step, the SiO₂ film is deposited by CVD using, forexample, SiCl₄ and O₂ as processing gases. During the deposition step,the flow rate of O₂ is gradually increased. For this reason, in thesequence of FIG. 9, the etching rate of the SiO₂ film formed on theprocessing target is gradually decreased (see, e.g., FIG. 4). During thedeposition step, the flow rate of SiCl₄ is constant. After thedeposition step, an etching step is performed by generating plasma fromNF₃ gas. As described above, in the plasma processing method accordingto Modification 1, the etching rate of one film is capable of beinggradually changed by changing the processing condition during thedeposition step. For example, in the plasma processing method, bygradually changing the ratio of a plurality of gases which arecomponents of the film, it is possible to deposit the film whilecontinuously changing the etching rate. In the plasma processing method,it is possible to gradually change the etching rate of one film byincreasing the flow rate of a predetermined gas.

<Processing Sequence Example 2>

FIG. 10 is a view illustrating another example of the processingsequence of the plasma processing according to Modification 1. In theexample of FIG. 10, a film is deposited using two types ofcarbon-containing gases as in the example of FIG. 6. However, unlike theexample of FIG. 6, in the example of FIG. 10, during the depositionstep, the flow rate of the second carbon-containing gas is graduallyincreased simultaneously with gradually decreasing the flow rate of thefirst carbon-containing gas. For this reason, the film to be depositedhas a strong nature of the first carbon-containing gas at the initiationof the processing, and gradually becomes a film having a strong propertyof the second carbon-containing gas. For example, as illustrated in FIG.6, when the etching rate of the first carbon film is higher than theetching rate of the second carbon film, carbon films, of which theetching rates are gradually lowered from the lower layer toward theupper layer, may be deposited by the processing illustrated in FIG. 10.In addition, the first carbon-containing gas is, for example, a CF-basedgas (e.g., C₄F₈ or C₄F₆) or a CHF-based gas (CH₂F₂ or CH₃F). The secondcarbon-containing gas is, for example, a CH-based gas (e.g., CH₄).

<Processing Sequence Example 3>

FIG. 11 is a view illustrating still another example of the processingsequence of the plasma processing according to Modification 1. In theexample of FIG. 11, the film is deposited using the same processing gasas the example of FIG. 7. However, unlike the example of FIG. 7, in theexample of FIG. 11, during the deposition step, the flow rates of SiCl₄and O₂ are gradually increased simultaneously with gradually decreasingthe carbon-containing gas. For this reason, the film to be deposited isa carbon film at the initiation of the processing, and the compositiongradually changes to a SiO₂ film. For this reason, by the processing ofFIG. 11, it is possible to deposit films, of which etching rates aregradually lowered from the lower layer toward the upper layer.

As in the first embodiment, each sequence of Modification 1 may berepeatedly executed for an arbitrary number of cycles until a desiredLCDU is achieved.

<Effect of Modification 1>

The plasma processing method according to Modification 1 includes adeposition step and an etching step. In the deposition step, the plasmaprocessing apparatus deposits a film on a processing target in which aplurality of openings having a predetermined patter are formed under thecondition that the etching rate decreases as the distance from theprocessing target increases and the deposited amount on the sidesurfaces of the openings varies according to the sizes of the openings.In the etching step, the plasma processing apparatus performs etching ofa processing target on which a film is deposited. For this reason,according to the plasma processing method of Modification 1, it ispossible to provide a difference in etching rate by depositing one filmwhile changing the processing conditions. For this reason, according tothe plasma processing method of Modification 1, it is possible toimprove the LCDU with a small number of steps.

In addition, according to the plasma processing method of Modification1, in the deposition step, the plasma processing apparatus deposits afilm of which the etching rate changes continuously by graduallychanging the ratio of a plurality of supplied gases. For example, theplasma processing apparatus gradually increases the oxygen content ofthe supplied gases. For this reason, according to Modification 1, theplasma processing apparatus is able to improve the LCDU by a simpleprocessing.

In the plasma processing method according to Modification 1, thedeposition step and the etching step are repeatedly performed until itis determined that a predetermined condition is satisfied. For thisreason, according to Modification 1, it is possible to improve the LCDUto a desired level.

<Modification 2—Adjustment of Etching Rate by Modification>

In Modification 1, the etching rate is changed in one film by changingthe flow rate of components in forming a film. In Modification 2, byperforming a modification processing on the formed film to turn the filminto form the first film, a difference is made between the first filmand the second film.

FIG. 12 is a flowchart illustrating an example of a flow of the plasmaprocessing according to Modification 2. The plasma processing accordingto Modification 2 is performed in, for example, a plasma processingapparatus described later (see, e.g., FIG. 15).

First, like the plasma processing according to the first embodiment(see, e.g., FIG. 1), a processing target (e.g., a wafer) in which aplurality of openings having a predetermined pattern are formed isdisposed in a space in which a plasma processing is to be performed. Theplasma processing apparatus executes a first step (step S1201). First,the plasma processing apparatus deposits a film on the pattern in thefirst step. Next, the plasma processing apparatus performs amodification processing on the deposited film. The modificationprocessing is a processing to increase the etching rate of the film bymodifying the film surface so as to be brittle. This forms the firstfilm. Next, the plasma processing apparatus executes a second step (stepS1202). In the second step, the plasma processing apparatus deposits asecond film on the first film by, for example, CVD. The second step isperformed under the condition that a loading effect is obtained, as inthe first embodiment. Next, the plasma processing apparatus executes anetching step (step S1203). Then, the plasma processing apparatusdetermines whether or not the processing target is in the state in whicha predetermined condition is satisfied (step S1204). When it isdetermined that the predetermined condition is not satisfied (No in stepS1204), the plasma processing apparatus returns to step S1201 andrepeats the processing. Meanwhile, when it is determined that thepredetermined condition is satisfied (Yes in step S1204), the plasmaprocessing apparatus terminates the processing. This is an example ofthe flow of the plasma processing according to Modification 2.

The modification processing is, for example, a processing of generatingplasma in the state in which a gas that is a raw material of the film isnot supplied. For example, in the first step, a nitride film (SiN) isdeposited first. Thereafter, the plasma of hydrogen (H₂) is generated,and the nitride film is exposed to the H plasma. Since this processingmakes the film surface brittle, the etching rate becomes high. However,the combination of the gas type when generating the plasma and the filmtype is not limited to this. For example, after depositing the oxidefilm (SiO₂) in the first step, the modification processing may beperformed by generating the plasma of hydrogen (H₂) and exposing theoxide film to the H plasma.

In addition, the modification processing may be performed using theloading effect or may be performed without using the loading effect. Inthe case of using the loading effect, the larger the opening dimension,the greater the degree of modification or the depth from the surface tobe modified. In the case of modifying the nitride film with the Hplasma, the degree of exposure to plasma becomes higher in a portionhaving a larger surface area. Thus, it is possible to increase thedegree of modification or the modification depth as the openingdimension becomes larger.

The plasma processing method according Modification 2 includes a firststep, a second step, and an etching step. In the first step, the plasmaprocessing apparatus forms a first film on a processing target in whicha plurality of openings having a predetermined pattern are formed. Inthe second step, the plasma processing apparatus forms a second filmhaving a lower etching rate than the first film on the processing targeton which the first film is formed, in which the film thicknesses on theside surfaces of the openings are different according to the sizes ofthe openings. In the etching step, the plasma processing apparatusperforms etching under a predetermined processing condition until aportion of the first film is removed from at least a portion of theprocessing target from above the second film. Then, in Modification 2,in the first step, the plasma processing apparatus forms the first filmhaving a higher etching rate than the second film by performing themodification processing on the film deposited on the processing target.The modification processing is, for example, a processing of exposing afilm to plasma under a predetermined process condition. Therefore,according to Modification 2, it is possible to make a difference inetching rate while depositing the same type of film as the first andsecond films.

<Modification 3—Formation of Second Film by Modification Processing>

In Modification 2, a difference is made between the etching rates of thefirst film and the second film by performing the modificationprocessing. In Modification 3, the film to be deposited is a singlelayer, and the modification processing is performed after the depositionof the film, thereby obtaining the same effect as depositing two filmshaving different etching rates.

FIG. 13 is a flowchart illustrating an example of a flow of a plasmaprocessing according to Modification 3. The plasma processing accordingto Modification 3 is performed in a plasma processing apparatusdescribed later (see, e.g., FIG. 15).

First, like the plasma processing according to the first embodiment(see, e.g., FIG. 1), a processing target (e.g., a wafer) in which aplurality of openings having a predetermined pattern are formed isdisposed in a space in which a plasma processing is to be performed. Theplasma processing apparatus executes a first step (step S1301). First,the plasma processing apparatus deposits a film on the pattern in thefirst step. The type of film deposited here is not particularly limited.However, the film to be deposited is formed by executing CVD using, forexample, the same type of gas without changing a processing conditionduring the processing. Next, the plasma processing apparatus executes asecond step (step S1302). In the second step, the plasma processingapparatus performs a modification processing on the film formed in thefirst step. The modification processing is a processing for lowering theetching rate of the surface of the film formed in the first step. Inaddition, the modification processing is performed under the conditionthat a loading effect is exhibited. That is, the modification processingis carried out under the condition that the degree of modification orthe depth from the surface to be modified increases as the openingdimension increases. Next, the plasma processing apparatus executes anetching step (step S1303). Then, the plasma processing apparatusdetermines whether or not the processing target is in the state in whicha predetermined condition is satisfied (step S1304). When it isdetermined that the predetermined condition is not satisfied (No in stepS1304), the plasma processing apparatus returns to step S1301 andrepeats the processing. Meanwhile, when it is determined that thepredetermined condition is satisfied (Yes in step S1304), the plasmaprocessing apparatus terminates the processing. This is an example ofthe flow of the plasma processing according to Modification 3.

FIG. 14 is a view illustrating an example of the processing sequence ofthe plasma processing according to Modification 3. In the example ofFIG. 14, after the first step (CVD), the plasma processing apparatusperforms a modification step as a second step. Thereafter, the plasmaprocessing apparatus performs an etching processing. In the first stepin the example of FIG. 14, the plasma processing apparatus deposits afilm using methane (CH₄) and octafluorocyclobutane (C₄F₈) as processinggases. In the next second step, the plasma processing apparatus stopssupply of CH₄ and C₄F₈ and supplies a rare gas such as, for example,argon (Ar) or helium (He), nitrogen (N₂), or hydrogen (H₂) so as togenerate plasma. The film deposited in the first step is compacted andincreased in density by being exposed to the plasma. Therefore, the filmis hardened in the second step, and thus the etching rate is lowered. Atthis time, since the degree of exposure of the film deposited in thefirst step is greater in a portion having a larger opening dimension,the degree of modification or the depth to be modified varies accordingto the opening dimension. For this reason, it is possible to obtain aloading effect, which is substantially the same as, for example, thefirst embodiment in which the second film is deposited using the loadingeffect. After the second step, the plasma processing apparatus suppliesO₂ to perform etching of the modified film.

The gas types that can be used in the processing illustrated in FIG. 14are not limited to C₄F₈ and CH₄. In the first step, for example, a filmmay be deposited using a type of gas containing silicon or carbon. Then,in the second step, supply of the type of gas containing silicon orcarbon is stopped, and then, for example, a rare gas (e.g., Ar),hydrogen gas (H₂), or nitrogen gas (N₂) is supplied to generate plasma.The CVD executed in the first step may be plasma CVD.

<Effect of Modification 3>

In the plasma processing method according to Modification 3, in thesecond step, a modification processing is performed on the first film soas to modify the first film, thereby forming the second film. Inaddition, the modification processing exposes the first film to theplasma under a processing condition that the depth from the surface tobe modified by the plasma or the degree of modification becomes greaterin an opening having a larger size. For this reason, according to theplasma processing method of Modification 3, it is possible to change theetching rate of a film by changing the property of the film using theloading effect. Therefore, according to Modification 3, it is possibleto obtain the same effect as, for example, the first embodiment or thelike in which two films are used, using one film.

In the plasma processing method according to Modification 3, thedeposition step and the etching step are repeatedly performed until itis determined that a predetermined condition is satisfied. Therefore,according to the plasma processing method of Modification 3, it ispossible to obtain a desired LCDU improvement effect by adjusting thenumber of repetitions of deposition and etching steps.

<Example of Plasma Processing Apparatus According to Embodiment>

The plasma processing methods according to the first embodiment, andModifications 1 to 3 may be performed using the plasma processingapparatus 1 described below.

Next, a substrate processing apparatus 1 according to an embodiment willbe described with reference to FIG. 15. FIG. 15 is a view illustratingan example of a vertical cross section of a plasma processing apparatus1 according to an embodiment. In the plasma etching apparatus 1according to the present embodiment, a desired plasma processing suchas, for example, plasma etching, film formation, or sputtering, isperformed on a semiconductor wafer. The plasma processing apparatus 1according to the present embodiment is a parallel flat plate type plasmaprocessing apparatus (capacitively coupled plasma processing apparatus)in which a stage 20 and a gas shower head 25 are disposed inside achamber 10 to face each other. The stage 20 also functions as a lowerelectrode, and the gas shower head 25 also functions as an upperelectrode.

The plasma etching apparatus 1 has a cylindrical chamber 10 made of, forexample, aluminum, of which the surface is subjected to an alumitetreatment (anodized). The chamber 10 is electrically grounded. The stage20 configured to place a semiconductor wafer (hereinafter simplyreferred to as a “wafer W”) thereon is provided on the bottom of thechamber 10. The wafer W is an example of a processing target. The stage20 includes an electrostatic chuck 106 configured to hold a wafer W byan electrostatic attraction force and a base 104 configured to supportthe electrostatic chuck 106. The base 104 is formed of, for example,aluminum (Al), titanium (Ti), or silicon carbide (SiC).

The electrostatic chuck 106 is provided on the upper surface of the base104 in order to electrostatically attract a wafer. The electrostaticchuck 106 has a structure in which a chuck electrode 106 a is sandwichedbetween insulators 106 b. A DC voltage source 112 is connected to thechuck electrode 106 a, and a DC voltage HV is applied from the DCvoltage source 112 to the chuck electrode 106 a, whereby the wafer W isattracted to the electrostatic chuck 106 by an electrostatic force. Onthe upper surface of the electrostatic chuck 106, a holding surfaceconfigured to hold the wafer W thereon and a peripheral edge portionwhich is lower than the holding surface are formed. The wafer W isplaced on the holding surface of the electrostatic chuck 106.Hereinafter, the holding surface of the electrostatic chuck 106 will beappropriately referred to as a “placement surface of the stage 20.”

A focus ring 108 is disposed on the peripheral edge portion of theelectrostatic chuck 106 so as to surround the wafer W placed on theplacement surface of the stage 20. The focus ring 108 is formed of, forexample, silicon or quartz. The focus ring 108 functions to enhancein-plane uniformity of etching.

In addition, inside the stage 20 (the base 104), a coolant flow path 104a is formed. A coolant inlet pipe 104 b and a coolant outlet pipe 104 care connected to the coolant flow path 104 a. A cooling medium(hereinafter, also referred to as “coolant”) such as, for example,cooling water or brine output from a chiller 107 circulates through thecoolant inlet pipe 104 b, the coolant flow path 104 a, and the coolantoutlet pipe 104 c. The stage 20 and the electrostatic chuck 106 arecooled by the coolant.

A heat transfer gas supply source 85 supplies a heat transfer gas suchas, for example, helium gas (He) or argon gas (Ar) through a gas supplyline 130 to the rear surface of the wafer W on the electrostatic chuck106. With such a configuration, the temperature of the electrostaticchuck 106 is controlled by the coolant circulated in the coolant flowpath 104 a and the heat transfer gas supplied to the rear surface of thewafer W.

The stage 20 is connected with a power supply apparatus 30 configured tosupply two-frequency superimposed power. The power supply device 30 mayinclude a first radio-frequency power supply 32 configured to supplyfirst radio-frequency power of a first frequency (radio-frequency powerfor plasma generation), a second radio-frequency power supply 34configured to supply second radio-frequency power of a second frequencylower than the first frequency (radio-frequency power for bias voltagegeneration). The first radio-frequency power supply 32 is electricallyconnected to the stage 20 via a first matcher 33. The secondradio-frequency power supply 34 is electrically connected to the stage20 via a second matcher 35. The first radio-frequency power supply 32applies, for example, first radio-frequency power of 40 MHz to the stage20. The second radio-frequency power supply 34 applies, for example,second radio-frequency power of 400 kHz to the stage 20. In the presentembodiment, the first radio-frequency power is applied to the stage 20.However, the first radio-frequency power may be applied to the gasshower head 25.

The first matcher 33 matches a load impedance to the internal (oroutput) impedance of the first radio-frequency power supply 32. Thesecond matcher 35 matches a load impedance to the internal (or output)impedance of the second radio-frequency power supply 34. The firstmatcher 33 functions such that the internal impedance of the firstradio-frequency power supply 32 apparently coincides with the loadimpedance when plasma is generated in the chamber 10. The second matcher35 functions such that the internal impedance of the secondradio-frequency power supply 34 apparently coincides with the loadimpedance when plasma is generated in the chamber 10.

The gas shower head 25 is attached so as to close the opening of theceiling portion of the chamber 10 via a shield ring 40 that covers theperipheral edge portion of the gas shower head 25. The gas shower head25 may be electrically grounded as illustrated in FIG. 15. In addition,a variable DC power supply may be connected to apply a predetermined DCvoltage to the gas shower head 25.

A gas introduction port 45 for introducing a gas is formed in the gasshower head 25. Inside the gas shower head 25, a center diffusionchamber 50 a and an edge diffusion chamber 50 b are branched from thegas introduction port 45. The gas output from the gas supply source 15is supplied to the diffusion chambers 50 a and 50 b via the gasintroduction port 45, diffused in the diffusion chambers 50 a and 50 b,and introduced from a large number of gas supply holes 55 toward thestage 20.

An exhaust port 60 is formed in the bottom of the chamber 10, and theinside of the chamber 10 is evacuated by an exhaust apparatus 65connected to the exhaust port 60. This makes it possible to maintain theinside of the chamber 10 at a predetermined degree of vacuum. On theside wall of the chamber 10, a gate valve G is provided. The gate valveG opens/closes a loading/unloading port when a wafer W isloaded/unloaded W into/from the chamber 10.

The plasma processing apparatus 1 is provided with a controller 100configured to control the overall operation of the apparatus. Thecontroller 100 includes a central processing unit (CPU) 105, a read onlymemory (ROM) 110, and a random-access memory (RAM) 115. According tovarious recipes stored in these storage areas, the CPU 105 executes adesired processing such as, for example, a plasma processing to bedescribed later. The recipes include, for example, process time,pressure (gas evacuation), radio-frequency power and voltage, variousgas flow rates, temperature in the chamber (upper electrode temperature,side wall temperature of the chamber, or wafer W temperature(electrostatic chuck temperature)), and the temperature of coolantoutput from the chiller 107. In addition, recipes representing theseprograms and processing conditions may be stored in a hard disk or asemiconductor memory. Further, the recipes may be set at a predeterminedposition in the state of being stored in a storage medium readable by aportable computer such as, for example, a CD-ROM or a DVD so as to beread out.

For example, the controller 100 controls each unit of the plasmaprocessing apparatus 1 so as to perform a plasma processing methoddescribed above.

Furthermore, the substrate processing apparatus according to the presentdisclosure is applicable not only to a capacitively coupled plasma (CCP)apparatus, but also to other substrate processing apparatuses. The othersubstrate processing apparatuses may be, for example, an inductivelycoupled plasma (ICP) apparatus, a plasma processing apparatus using aradial line slot antenna, a helicon wave plasma (HWP) apparatus, and anelectron cyclotron resonance (ECR) plasma apparatus.

According to the present disclosure, it is possible to improve LCDU.

From the foregoing, it will be appreciated that various embodiments ofthe present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

What is claimed is:
 1. A plasma processing method comprising: (a)providing a substrate which includes a processing target and a patternhaving a plurality of openings; (b) forming a first film on the pattern;(c) forming a second film on the first film, the second film having anetching rate lower than that of the first film, and the second filmhaving different film thicknesses on side surfaces of the openingsaccording to sizes of the openings; and (d) etching the second filmunder a predetermined processing condition until a portion of the firstfilm is removed from at least a portion of the processing target,wherein the providing the substrate includes providing the substrate inwhich the plurality of openings include a first opening and a secondopening, and the first opening has an opening size different from anopening size of the second opening, and wherein after the etching of thesecond film a difference in opening size between the first opening andthe second opening is reduced compared to prior to the forming of thefirst film.
 2. The plasma processing method according to claim 1,wherein the forming of the first film includes depositing a material ofthe first film and modifying the material to form the first film with anetching rate higher than that of the second film.
 3. The plasmaprocessing method according to claim 2, wherein the modifying of thematerial of the first film includes exposing the material to a plasma.4. The plasma processing method according to claim 1, wherein theforming of the second film includes modifying a portion of a material ofthe first film to form the second film.
 5. The plasma processing methodaccording to claim 4, wherein the modifying of the portion of thematerial of the first film includes exposing the material of the firstfilm to the plasma under a processing condition in which (i) a depthfrom a surface of the material which is modified by the plasma isgreater in an opening having a larger size, or (ii) a degree of themodification of the material is greater in an opening having a largersize.
 6. The plasma processing method according to claim 5, wherein, inthe etching of the second film, the predetermined processing conditionis changed from a first processing condition to a second processingcondition at a time when the first film is exposed in at least a portionof the processing target.
 7. The plasma processing method according toclaim 6, further comprising: repeating (b) to (d) until thepredetermined condition is satisfied.
 8. The plasma processing methodaccording to claim 1, wherein, in the etching of the second film, thepredetermined processing condition is changed from a first processingcondition to a second processing condition at a time when the first filmis exposed in at least a portion of the processing target.
 9. The plasmaprocessing method according to claim 1, further comprising: repeating(b) to (d) until the predetermined condition is satisfied.
 10. Theplasma processing method according to claim 1, wherein the difference inopening size between the first opening and the second opening is reducedafter the forming of the second film compared to prior to forming of thefirst film, and the difference in opening size is further reduced afterthe etching of the second film.
 11. A plasma processing methodcomprising: (a) providing a substrate which includes a processing targetand a pattern having a plurality of openings; (b) depositing a film onside surfaces of the openings under a processing condition which formsportions with different etch rates and in which an etching ratedecreases as a distance from the side surfaces increases and a depositedamount on side surfaces of the openings varies according to sizes of theopenings; and (c) etching the processing target on which the film isdeposited, wherein the providing the substrate includes providing thesubstrate in which the plurality of openings include a first opening anda second opening, and the first opening has an opening size differentfrom an opening size of the second opening, and wherein a difference inthe opening size between the first opening and the second opening isreduced after the depositing of the film compared to prior to thedepositing of the film.
 12. The plasma processing method according toclaim 11, wherein the depositing of the film includes changing a supplyratio of a plurality of gases to deposit the film with a continuouslyvarying etching rate.
 13. The plasma processing method according toclaim 12, wherein the changing of the supply ratio includes increasingan oxygen content of the gases.
 14. The plasma processing methodaccording to claim 13, further comprising: repeating (b) and (c) until apredetermined condition is satisfied.
 15. The plasma processing methodaccording to claim 11, further comprising: repeating (b) and (c) until apredetermined condition is satisfied.